Demonstration by lectin-gold cytochemistry of transfer of glycoconjugates of oviductal origin to the zona pellucida of oocytes after ovulation in hamsters

Mysteries and unsolved problems of mammalian fertilization and related topics

Mammalian fertilization is a fascinating process that leads to the formation of a new individual. Eggs and sperm are complex cells that must meet at the appropriate time and position within the female reproductive tract for successful fertilization. I have been studying various aspects of mammalian fertilization over 60 years. In this review, I discuss many different aspects of mammalian fertilization, some of my laboratory's contribution to the field, and discuss enigmas and mysteries that remain to be solved.

The role of oviduct-specific glycoprotein (OVGP1) in modulating biological functions of gametes and embryos

Diverse lines of evidence indicate that the mammalian oviduct makes important contributions to the complex process of reproduction other than being simply a conduit for the transport of gametes and embryos. The cumulative synthesis and transport of proteins secreted by oviductal secretory cells into the oviductal lumen create a microenvironment supporting important reproductive events, including sperm capacitation, fertilization, and early embryo development. Among the components that have been identified in the oviductal fluid is a family of glycosylated proteins known collectively as oviduct-specific glycoprotein (OVGP1) or oviductin. OVGP1 has been identified in several mammalian species, including humans. The present review summarizes the work carried out, in various mammalian species, by many research groups revealing the synthesis and secretion of OVGP1, its fate in the female reproductive tract upon secretion by the oviductal epithelium, and its role in modulating biological functions of gametes and embryos. The production and functions of recombinant human OVGP1 and recombinant OVGP1 of other mammalian species are also discussed. Some of the findings obtained with immunocytochemistry will be highlighted in the present review. It is hoped that the findings obtained from recent studies carried out with recombinant OVGP1 from various species will rekindle researchers’ interest in pursuing further the role of the oviductal microenvironment, of which OVGP1 is a major component, in contributing to the successful occurrence of early reproductive events, and the potential use of OVGP1 in improving the current assisted reproductive technology in alleviating infertility.

A Comparative View on the Oviductal Environment during the Periconception Period

The oviduct plays important roles in reproductive events: sperm reservoir formation, final gamete maturation, fertilization and early embryo development. It is well known that the oviductal environment affects gametes and embryos and, ultimately, the health of offspring, so that in vivo embryos are better in terms of morphology, cryotolerance, pregnancy rates or epigenetic profile than those obtained in vitro. The deciphering of embryo-maternal interaction in the oviduct may provide a better understanding of the embryo needs during the periconception period to improve reproductive efficiency. Here, we perform a comparative analysis among species of oviductal gene expression related to embryonic development during its journey through the oviduct, as described to date. Cross-talk communication between the oviduct environment and embryo will be studied by analyses of the secreted or exosomal proteins of the oviduct and the presence of receptors in the membrane of the embryo blastomeres. Finally, we review the data that are available to date on the expression and characterization of the most abundant protein in the oviduct, oviductin (OVGP1), highlighting its fundamental role in fertilization and embryonic development.

Modifications of carbohydrate residues in the sheep oviductal ampulla after superovulation

Epithelium of oviductal ampulla was studied in normal and in superovulated sheep using morphologic analysis and lectin glycohistochemistry. The lining epithelium consisted of two types of cells, ciliated and nonciliated cells. Unlike superovulated samples, the nonciliated cells from control ewes showed apical protrusions indicating an apocrine secretory activity. The ciliated cells showed lectin-binding sites mainly at the level of the cilia which bound all the used lectins except Peanut agglutinin, suggesting the lack of glycans terminating with Galβ1,3GalNAc. In superovulated specimens, the ciliated cells with high mannosylated glycans Concanavalin A (Con A) and GlcNAc and GalNac termini Griffonia simplicifolia agglutinin II (GSA II) and Dolicurus biflorus agglutinin (DBA) decreased. The luminal surface of nonciliated cells showed all investigated sugar residues in controls, whereas it was lacking in high mannosylated (Con A) and terminal GalNAcα1,3(LFucα1,2)Galβ1,3/4GlcNAcβ1 sequence (DBA) in superovulated ewes. Apical protrusions from control ampullae nonciliated cells showed glycans containing mannose, GlcNac, GalNAc, galactose, and α2,3-linked sialic acid (Con A, KOH-sialidase- Wheat germ agglutnin [WGA], GSA II, SBA, Griffonia simplicifolia agglutinin-isolectin B4 [GSA I-B4], Maackia amurensis agglutinin II [MAL II]). The supranuclear cytoplasm of nonciliated cells expressed terminal GlcNAc (GSA II) in all specimens, also O-linked glycans (mucin-type glycans) with GalNAc and sialic acid termini (Helix pomatia agglutinin [HPA] and MAL II) in control animals, and also N-linked glycans with fucose, galactose, lactosamine, and α2,3-linked sialic acid termini (Ulex europaeus agglutinin I [UEA I], GSA I-B4, Ricinus communis agglutinin120 [RCA120], and Sambucus nigra agglutinin [SNA] ) in superovulated ewes. These results report for the first time that the superovulation treatment affects the secretory activity and the glycan pattern of the epithelium lining the sheep oviductal ampulla.

Morphometric and ultrastructural features of the mare oviduct epithelium during oestrus

Morphometric, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations have displayed regional differences in the mare oviductal epithelium. The entire mucosa of the oviduct was lined with a pseudostratified epithelium, which consisted of two distinct cell types, ciliated and non-ciliated. Ciliated cells were predominant in the three different segments of the oviduct and their percentage increased from fimbriae to ampulla and significantly decreased in the isthmus. SEM revealed in the infundibulum finger-like mucosal folds, some of them interconnected, in the ampulla numerous and elaborated branched folds of the mucosa, whereas the isthmus displayed a narrow lumen, short and non-branched mucosal folds. In the ampulla and isthmus the majority of non-ciliated cells showed apical blebs provided or not of short microvilli. TEM displayed different ultrastructural features of ciliated and non-ciliated cells along the oviduct. Isthmus ciliated cells presented a more electron-dense cytoplasm than in infundibulum and ampulla cells and its cilia were enclosed in an amorphous matrix. The non-ciliated cells of infundibulum did not contain secretory granules but some apical endocytic vesicles and microvilli coated by a well developed glycocalyx. Non-ciliated cells of ampulla and isthmus contained secretory granules. Apical protrusions of ampulla displayed two types of secretory granules as well as occasional electron-lucent vesicles. Isthmus non-ciliated cells showed either electron-lucent or electron-dense cytoplasm and not all contained apical protrusions. The electron-dense non-ciliated cells displayed microvilli coated with a well developed glycocalyx. Three types of granules were observed in the isthmus non-ciliated cells. The regional differences observed along the epithelium lining the mare oviduct suggest that the epithelium of the each segment is involved in the production of a distinctive microenvironment with a unique biochemical milieu related to its functional role.

What controls polyspermy in mammals, the oviduct or the oocyte?

A block to polyspermy is required for successful fertilisation and embryo survival in mammals. A higher incidence of polyspermy is observed during in vitro fertilisation (IVF) compared with the in vivo situation in several species. Two groups of mechanisms have traditionally been proposed as contributing to the block to polyspermy in mammals: oviduct-based mechanisms, avoiding a massive arrival of spermatozoa in the proximity of the oocyte, and egg-based mechanisms, including changes in the membrane and zona pellucida (ZP) in reaction to the fertilising sperm. Additionally, a mechanism has been described recently which involves modifications of the ZP in the oviduct before the oocyte interacts with spermatozoa, termed "pre-fertilisation zona pellucida hardening". This mechanism is mediated by the oviductal-specific glycoprotein (OVGP1) secreted by the oviductal epithelial cells around the time of ovulation, and is reinforced by heparin-like glycosaminoglycans (S-GAGs) present in oviductal fluid. Identification of the molecules contributing to the ZP modifications in the oviduct will improve our knowledge of the mechanisms of sperm-egg interaction and could help to increase the success of IVF systems in domestic animals and humans.

Oviduct-specific glycoprotein and heparin modulate sperm-zona pellucida interaction during fertilization and contribute to the control of polyspermy

Polyspermy is an important anomaly of fertilization in placental mammals, causing premature death of the embryo. It is especially frequent under in vitro conditions, complicating the successful generation of viable embryos. A block to polyspermy develops as a result of changes after sperm entry (i.e., cortical granule exocytosis). However, additional factors may play an important role in regulating polyspermy by acting on gametes before sperm-oocyte interaction. Most studies have used rodents as models, but ungulates may differ in mechanisms preventing polyspermy. We hypothesize that zona pellucida (ZP) changes during transit of the oocyte along the oviductal ampulla modulate the interaction with spermatozoa, contributing to the regulation of polyspermy. We report here that periovulatory oviductal fluid (OF) from sows and heifers increases (both, con- and heterospecifically) ZP resistance to digestion with pronase (a parameter commonly used to measure the block to polyspermy), changing from digestion times of approximately 1 min (pig) or 2 min (cattle) to 45 min (pig) or several hours (cattle). Exposure of oocytes to OF increases monospermy after in vitro fertilization in both species, and in pigs, sperm-ZP binding decreases. The resistance of OF-exposed oocytes to pronase was abolished by exposure to heparin-depleted medium; in a medium with heparin it was not altered. Proteomic analysis of the content released in the heparin-depleted medium after removal of OF-exposed oocytes allowed the isolation and identification of oviduct-specific glycoprotein. Thus, an oviduct-specific glycoprotein-heparin protein complex seems to be responsible for ZP changes in the oviduct before fertilization, affecting sperm binding and contributing to the regulation of polyspermy.

Intracellular responses and morphology of rat ventral complex of the lateral lemniscus neurons in vivo

The function of the ventral and intermediate nuclei of the lateral lemniscus (VNLL and INLL), collectively termed ventral complex of the lateral lemniscus (VCLL), is unclear. Several studies have suggested that it plays a role in coding the temporal aspects of sound. In our study, a sample (n = 161) of intracellular responses to dichotically presented noise or tone bursts was collected from the VCLL of urethane-anesthetized rats in vivo. Intracellular recordings revealed six distinct response types to tones, distinguished by their synaptic and membrane characteristics as well as firing pattern. Three of these response types were correlated with distinct cellular morphologies revealed by intracellular injection of neurobiotin. 3D reconstructions of recorded neurons within the VCLL showed the spatial distribution of various response properties, including response type, laterality, characteristic frequency (CF), and binaural influences. Cells that responded to monaural (55%) or binaural (45%) stimulation were distributed throughout the VCLL. Almost all VCLL units were responsive to contralateral stimulation (97%). Most neurons were excited by contralateral stimulation (83%), many exclusively (43%), and some in conjunction with ipsilateral inhibition (28%) or excitation (12%). The INLL contained mostly binaural neurons (65%), typically with ipsilateral inhibition and contralateral excitation. These results indicate that the VCLL is not a monaural structure and there is a dorsal-ventral segregation of binaural and monaural cells. 3D reconstructions of intracellular CFs did not reveal the presence of any tonotopic arrangement within the VCLL. Presumably, the proposed timing role of this structure does not require a systematic representation of tonal frequency.

Identification of novel gamete receptors that mediate sperm adhesion to the egg coat

Mammalian fertilization is initiated by the species-specific binding of sperm to the zona pellucida, or egg coat. Earlier studies suggested that sperm-egg adhesion in mouse is mediated by the binding of beta1,4-galactosyltransferase-I (GalT) on the sperm surface to specific glycoside ligands on the egg coat glycoprotein, ZP3. Binding of multiple ZP3 oligosaccharides induces GalT aggregation, triggering a pertussis toxin-sensitive G-protein cascade leading to induction of the acrosome reaction. Consistent with this, sperm bearing targeted deletions in GalT are unable to bind ZP3 nor undergo ZP3-dependent acrosomal exocytosis; however, GalT-null sperm are still able to bind to the egg coat. This indicates that sperm-egg binding requires at least two independent binding mechanisms: a GalT-ZP3-independent event that mediates initial adhesion, followed by a GalT-ZP3 interaction that facilitates acrosomal exocytosis. During the past few years, novel GalT-ZP3-independent gamete receptors have been identified that appear to participate in initial gamete adhesion. On such receptor is SED1, an EGF repeat and discoidin domain protein that coats sperm as they traverse through the epididymis, and which is required for sperm to bind the egg coat. Similarly, a novel egg coat ligand is present on ovulated oocytes, but not on ovarian eggs, and which also appears to function in initial sperm binding. The identification of novel gamete receptors that are required for sperm-egg binding opens up new avenues for the development of specific contraceptive strategies.

Detection of nascent and/or mature forms of oviductin in the female reproductive tract and post-ovulatory oocytes by use of a polyclonal antibody against recombinant hamster oviductin

Oviductins belong to a family of glycoproteins that have been suggested to play several roles during the early processes of reproduction. Recently, a polyclonal antibody was raised against recombinant hamster oviductin (rhaOv(m)). Here the anti-rhaOv(m) antibody was used to investigate the sites of localization of oviductin in the female golden hamster. In the hamster oviduct, immunolabeling was restricted to the content of the Golgi saccules and secretory granules of the non-ciliated oviduct cells. After its release into the lumen, oviductin becomes associated with the zona pellucida of post-ovulatory oocytes. In unfertilized oocytes, oviductin was also detected in membrane invaginations along the oolemma and in some vesicles within the ooplasm. Furthermore, oviductin was detected over the microvilli and within multivesicular bodies of uterine epithelial cells. Western blotting analysis revealed the presence of oviductin in the hamster oviduct but not in the uterus or ovary. In the oviduct, the anti-rhaOv(m) antibody detected a polydispersed band corresponding to native oviductin (160-350 kD) and several lower molecular weight bands (<100 kD) corresponding to nascent and partially glycosylated forms of oviductin. The anti-rhaOv(m) antibody provides an additional tool for investigation into the cytochemical and biochemical properties of different forms of hamster oviductin in the female reproductive tract.

Characterization of a novel ZP3-independent sperm-binding ligand that facilitates sperm adhesion to the egg coat

During mammalian fertilization, sperm adhere to the extracellular coat of the egg, or zona pellucida, in a species-specific manner. In mouse, evidence suggests that sperm recognize and bind to specific oligosaccharide ligands within the zona pellucida glycoprotein, ZP3, viaβ1,4-galactosyltransferase I (GalT I), a lectin-like receptor on the sperm surface. Although in vitro experiments using isolated gametes lend support to this model, recent in vivo studies of genetically altered mice question whether ZP3 and/or GalT I are solely responsible for sperm-egg binding. In this regard, sperm from GalT I-null mice bind poorly to ZP3 and fail to undergo a zona-induced acrosome reaction; however, they still bind to the ovulated egg coat in vitro.

In this report, we characterize a novel ZP3- and GalT I-independent mechanism for sperm adhesion to the egg coat. Results show that the ovulated zona pellucida contains at least two distinct ligands for sperm binding: a ZP3-independent ligand that is peripherally associated with the egg coat and facilitates gamete adhesion; and a ZP3-dependent ligand that is present in the insoluble zona matrix and is recognized by sperm GalT I to facilitate acrosomal exocytosis. The ZP3-independent ligand is not a result of contamination by egg cortical granules, nor is it the mouse homolog of oviduct-specific glycoprotein. It behaves as a 250 kDa, WGA-reactive glycoprotein with a basic isoelectric point, distinguishing it from the acidic glycoproteins that form the insoluble matrix of the egg coat. When eluted from isoelectric focusing gels, the acidic matrix glycoproteins possess sperm-binding activity for wild-type sperm, but not for GalT I-null sperm,whereas the basic glycoprotein retains sperm-binding activity for both wild-type and GalT I-null sperm. Thus, GalT I-null sperm are able to resolve gamete recognition into at least two distinct binding events, leading to the characterization of a novel, peripherally associated, sperm-binding ligand on the ovulated zona pellucida.

Overexpression of monkey oviductal protein: purification and characterization of recombinant protein and its antibodies

The secretory cells lining the lumen of the mammalian oviduct synthesize and secrete high molecular weight glycoprotein (OGP). Molecular cDNA cloning of most of the mammalian OGP has been accomplished. The nucleotide and deduced amino acid sequences show a remarkable homology across species and also to chitinase protein. Even though OGP has been shown to interact with gametes and the early embryo, the protein's direct function has not yet been established. A prerequisite for such studies is the availability of well-characterized protein in bulk. We used recombinant DNA technology to obtain OGP (rOGP). An authentic partial cDNA clone encoding bonnet monkey (Macaca radiata) OGP (accession number AF132 215) was recloned into expression vector pET20b. Overexpression of the protein could be demonstrated after induction with isopropylthio-beta-galactopyranoside. Recombinant protein was purified by gel filtration of Escherichia coli lysate through Sephadex G75. The protein migrated with a molecular weight of approximately 14 kDa on SDS-PAGE. The molecular weight as assessed by matrix-assisted laser adsorption time-of-flight was 14 439 daltons. With Western blot procedures the protein could be immunostained with antibodies to human OGP, baboon OGP, and antipeptide antibodies generated against a well-conserved region of mammalian OGP. The monospecificity of rabbit antibodies generated against rOGP was established by its ability to immunostain human OGP (100-110 kDa) isolated from hydrosalpinx by Western blot analysis, and the antibody immunostained epithelial cells that secrete OGP in human fallopian tubes. OGP binding sites on the head and tail region of monkey sperm could be demonstrated by using antibody against rOGP.

In vivo versus in vitro oviductal glycoprotein (OGP) association with the zona pellucida (ZP) in the hamster and baboon

The goal of this study was to determine if differences exist between in vivo vs. in vitro OGP association with the ZP and to quantitate those differences. Ovarian oocytes were harvested 12.5 or 27 hr post-hCG from hyperstimulated hamsters or baboons, respectively. Hamster and baboon ovarian oocytes were incubated in vitro in media +/- homologous OGP (100 or 200 microg/100 microl) or in some studies with 100 microl oviductal fluid for 3, 6, or 24 hr at 37 degrees C. Some of the baboon ovarian oocytes were transferred immediately after harvesting to the ampulla of both oviducts using a tom cat catheter and retrieved after a 3 hr in situ incubation. Hamster oviductal oocytes were collected 3, 6, and 24 hr following ovulation. After incubation or oocyte retrieval from the oviduct, cumulus cells were removed, oocytes were washed extensively and binding of OGP to the ZP was examined by immunofluorescence. Fluorescence intensity was quantified using densitometric scanning of photographic negatives with the background of each negative as an internal control. In all studies, OGP association with the ZP was significantly greater in vivo than in vitro (P < 0.05). In vitro OGP association with the ZP did not significantly increase with incubation time or OGP concentration; however, a small nonsignificant increase in OGP association with the ZP in the oviduct was detected over time. Differences did not appear to be due to depletion of OGP from the in vitro incubation media, since Western blot analysis of the media showed that OGP was still present. Although OGP concentration in vivo is unknown, Western blots showed similar intensity comparing 100 microg of OGP media and oviductal fluid. Immunolocalization of OGP using laser confocal microscopy showed regional differences in OGP binding. The outer half of the zona pellucida had significantly more OGP bound than the inner half on oviductal oocytes. No regional differences were detected for in vitro incubated oocytes. In conclusion, OGP association with the ZP is greater in vivo vs. in vitro, suggesting that one must be cautious in designing and evaluating in vitro studies of OGP function.

Distribution of lectin-binding glycosidic residues in the hamster follicular oocytes and their modifications in the zona pellucida after ovulation

In the present study, we have employed a battery of colloidal gold-tagged lectins as probes in conjunction with quantitative analysis to demonstrate the distribution and changes of carbohydrate residues in the hamster zona pellucida (ZP) during ovarian follicular development and during transit of the oocyte through the oviduct after ovulation. High-resolution lectin-gold cytochemistry performed on thin sections of LR White-embedded ovaries revealed a moderate to strong reactivity to WGA, PNA, DSA, AAA, and MAA over the entire thickness of the ZP of ovarian oocytes at different stages of follicular development. Labeling intensity over the ZP progressively increased as follicles matured in the ovary. In parallel, there was an association of labeling by gold particles with cortical granules, stacks of Golgi saccules, and complex structures called vesicular aggregates in the oocyte proper especially during the late stages of follicular growth. In contrary, labeling with each of HPA, DBA, and BSAIB(4) was absent in the ovary but was found to be localized over Golgi complexes and secretory granules in the non-ciliated secretory cells of the oviduct. When ovulated oocytes were labeled with each of HPA, WGA, RCA-I, PNA, DSA, BSAIB(4), AAA, MAA, and DBA, the ZP and several organelles in the oocyte proper presented a differential distribution of lectin-binding sites. Quantitative analysis was also performed on labeling by lectin-gold complexes that bind specifically to the ZP of mature follicular and ovulated oocytes. Quantitative evaluation revealed heterogeneous labeling between the inner and the outer zone of the ZP. A significant increase in the labeling densities in both inner and outer ZP was noted when tissue sections of ovulated oocytes were labeled with RCA-I or AAA. Tissue sections of ovaries labeled with WGA demonstrated a significant increase in the density of labeling in the outer layer of the ZP. Labeling by PNA, DSA, and MAA, however, showed a significant decrease in both the inner and outer portions of the ZP. Together, these results suggest that in the hamster, glycoproteins carrying specific sugar residues are added to the ZP of ovarian follicles during the early stages of folliculogenesis and are processed through a common secretory machinery, and that there is a significant change in both the sugar moieties and distribution of glycoproteins in the ZP following ovulation. Our results also showed that the hamster oviduct plays an important role in contributing certain glycoproteins to the ZP suggesting that the sugar moieties of these oviductal glycoproteins may have functional significance in fertilization.

Differential expression of glycoside residues in the mammalian zona pellucida

The mammalian zona pellucida is an extracellular matrix surrounding the oocyte, and is composed of three major glycoproteins, ZP1, ZP2, and ZP3. Previous studies have suggested that the sperm receptor activity of the zona pellucida resides in specific oligosaccharide chains on the ZP3 glycoprotein. However, the nature of the terminal monosaccharide(s) on these glycosidic chains to which sperm bind is a matter of active debate. Evidence has been presented to support a role for at least three distinct monosaccharides in sperm binding, alpha-galactose, L-fucose on Lewis X structures, and beta-N-acetylglucosamine. Previous studies have shown that beta-N-acetylglucosamine is uniformly distributed throughout the zona matrix. In this study, we have investigated the expression and distribution of alpha-galactose and fucose moieties during the maturation of the zona pellucida in mouse, rat, and hamster. Interestingly, alpha-galactose residues are expressed only during later stages of zona secretion and, consequently, are confined to the inner portions of the mature zona pellucida in mouse and rat. In hamster, alpha-galactose residues are only detectable in the zona pellucida of ovulated eggs, and are not found in ovarian oocytes. Fucosyl residues linked to Lewis X glycosides are not detectable at any stage of zona maturation in these three species, whereas fucose linked to N-linked core oligosaccharides are present throughout the zona. These studies indicate a previously unappreciated heterogeneity in the composition of zona glycosides. The specific localization of alpha-galactose residues to the inner portions of the zona matrix suggest a role in the later stages of sperm penetration through the zona. Finally, due to their absence from the zona surface, alpha-galactose and Lewis X fucosyl residues are not likely to be mediators of primary sperm binding.

Ultrastructural and ultracytochemical features of secretory granules in the ampullary epithelium of the hamster oviduct

The epithelium of mammalian oviducts consists mainly of ciliated and non-ciliated secretory cells. In some mammals, secretory products originating from oviductal secretory cells have been shown to bind to the surface of, or accumulate within, ovulated eggs and/or developing embryos. These findings suggest that the secretions of the oviductal epithelial cells may play an important role in reproductive and developmental events that occur in the oviduct. In the present study, ultrastructural and cytochemical features of secretory cells in the hamster ampullary epithelium were shown by routine electron microscopy, lectin-gold cytochemistry and both conventional freeze-fracture and rapid-freezing techniques with special reference to the organizational aspects of their secretory granules. The use of ferrocyanide-reduced osmium tetroxide as a post-fixative in the Epon embedment of ampullary tissue samples also proved to be advantageous especially in revealing the carbohydrate contents of certain cellular compartments. The most conspicuous characteristic of the secretory cells, based on their staining property, was the presence of two types of secretory granules: those with a homogeneous electron-dense matrix and those with an electron-lucent matrix. Under favorable conditions, distinct features of the organizational arrangement of a crystalline lattice inside the secretory granules were also revealed. This well organized crystalline lattice shown in sections of Epon-embedded oviductal tissue was confirmed by examination of replicas of freeze-fractured oviducts prepared by the rapid-freezing technique. We also demonstrated with high resolution lectin-gold cytochemistry the intracellular distribution of lectin-binding glycoconjugates in the secretory cells of the hamster oviductal ampulla often in a linear array following the crystalline lattice. The results obtained in this study, taken together, provide insight into a possible link of the internal topographical features of oviductal secretory granules along with the cytochemical properties of their contents to the anticipated regulatory mechanism underlying their process of secretions.

Effects of stimulus frequency and intensity on c-fos mRNA expression in the adult rat auditory brainstem

Induction of the cellular fos gene (c-fos) is one of the earliest transcriptional changes observed following neuronal excitation. Although not an activity marker in the strict electrophysiological sense, many neurons in the central nervous system increase their c-fos expression after periods of sustained stimulation at physiological levels of intensity. In the present study, induction of c-fos mRNA expression was examined in the auditory brainstem after 1 hour of continuous free-field acoustic stimulation. Sprague-Dawley rats were exposed to pure tones of 2, 8, 16, or 32 kHz or half-octave noise bands centered on 2, 8, or 32 kHz at 80-120 dB SPL. Stimulation-induced c-fos mRNA expression was evident at all levels of the auditory brainstem, and this expression was intensity dependent. In some brain areas, induced expression manifested a clear tonotopic organization, i.e., in dorsal, posteroventral, and anteroventral cochlear nuclei, and in the medial nucleus of the trapezoid body. The inferior colliculus exhibited multiple tonotopic representations. The dorsal nucleus of the lateral lemniscus had a crude tonotopy. Although expression was present, tonotopy was not evident in periolivary nuclei or in the ventral or intermediate nuclei of the lateral lemniscus. Free-field diotic stimulation did not induce c-fos mRNA expression in the medial or lateral superior olivary nuclei. Expression was induced in the lateral superior olive by dichotic stimulation (after a unilateral cochlear ablation), and that expression was tonotopically organized. The results suggest that stimulation-induced c-fos mRNA expression can be an effective way of mapping neuronal activity in the central auditory system under both normal and pathological conditions.

Lack of topography in the ventral nucleus of the lateral lemniscus

In contrast to the ease of finding tonotopicity in other nuclei, both anatomical and electrophysiological methods have failed to demonstrate a clear and simple tonotopic map within the ventral nucleus of the lateral lemniscus (VLL). The present study was undertaken in cat with the hope that methods not used previously in studies of VLL might succeed in demonstrating an orderliness in its exiting fibers (i.e., efferents) or its incoming fibers (i.e., afferents). Since the same organization of ascending frequencies present in the cochlea is maintained in these fibers as well as in all main auditory nuclei, demonstration of a similar organization of frequencies in VLL would be evidence of the cochleo- or tono-topicity of this nucleus. Using triple injection of 3 different fluorescent dyes in inferior colliculus to study efferents, orderly and tonotopic cell-labeling is found in each of the brainstem auditory nuclei, with the notable exception of VLL. Instead, labeling of cell clusters, each cluster containing a small number of cells, is found randomly distributed throughout VLL in all 3 of its spatial dimensions. Using the 2-deoxyglucose (2-DG) method, during stimulation at 6 different frequencies, afferent orderliness, indeed, tonotopicity is found in all major brainstem auditory nuclei, again with the notable exception of VLL. Rather, each frequency evokes 2-DG label throughout VLL. In agreement with the results based on electrophysiological methods, therefore, the anatomical methods used here also yield no evidence of tonotopicity in VLL. Thus, if there is orderliness in VLL's efferents or afferents, it is based on an auditory dimension incommensurate with frequency.

Cholelithiasis induced in the Syrian hamster: evidence for an intramucinous nucleating process and down regulation of cholesterol 7 alpha-hydroxylase (CYP7) gene by medroxyprogesterone

This report reviews previously published studies from our laboratory and shows some recent morphological data obtained with scanning and transmission electron microscopy regarding gallstone formation and alteration of the gallbladder epithelium in the Syrian hamster model. Both male and female hamsters were treated with female sex steroids (estradiol alone, estradiol and medroxyprogesterone, medroxyprogesterone alone) during one month. The results show that the Syrian hamster is a good model to study bile changes, gallbladder structure changes, including gallstone formation, and the regulation of cholesterol metabolism at the molecular level. Arguments in favor of this animal model are presented and, during gallstone formation, epithelial cell changes, anionic mucus secretion, and formation of gallbladder luminal deposits can be demonstrated. Recent molecular biology observations related to the effect of female sex steroids on liver cholesterol 7 alpha-hydroxylase (CYP7) gene suggest that progestin alone or primed by estrogen down regulates CYP7 transcription and activity. In addition, progesterone in cell culture systems has been shown to enhance intracellular accumulation of free cholesterol by increasing its uptake and synthesis and by decreasing its esterification by inhibiting the activity of acylcoenzyme A: cholesterol acyltransferase. Non-esterified cholesterol is free to migrate to the extracellular spaces and may contribute to nucleation within the bile. It is suggested that these effects of progesterone on cholesterol metabolism combined with the CYP7 gene down regulation, physical changes in the mucus and the hypomotility of the gallbladder and biliary ducts result in hypersaturation of cholesterol in the bile which favors gallstone formation.

Post-fertilization changes in the zona pellucida glycoproteins of rat eggs

The zona pellucida (ZP) is the extracellular coat surrounding the mammalian egg. Numerous evidence supports the role of ZP carbohydrate residues as the specific sperm receptors. In this study we used lectins to study different distribution patterns of carbohydrate residues in the rat ZP, and to follow changes at fertilization. ZP were collected from follicular, ovulated, and fertilized eggs, incubated with one of 11 different biotin-labeled lectins, followed by avidin-fluorescein isothiocyanate (FITC) complex, and visualized by epifluorescent microscopy. For electron microscope (EM) histochemistry, eggs were embedded in LR white and ultrathin sections were stained with the complex Ricinus communis lectin (RCA-1)-colloidal gold. Some lectins (RCA-I, Glycine max) bound to the entire ZP while others were restricted to the inner or outer zones [Griffonia simplicifolia, Concanovalia ensiformis, Triticum vulgaris (WGA), succinyl-WGA]. Other lectins (Lens culinaris, Ulex europhaeus) were totally excluded. The RCA-1 binding pattern changed following sperm penetration, from homogeneous in ZP of ovulated eggs (57%) to uneven in ZP of fertilized (71%) or activated (68%) eggs. Our results demonstrate an uneven distribution of different sugar residues in the rat ZP, and a post-fertilization change in the distribution of beta-galactose, which is specifically recognized by RCA-I, presumably correlated with other changes in the ZP that lead to the block to polyspermy.

Anatomy of the ventral nucleus of the lateral lemniscus in rats: a nucleus with a concentric laminar organization

The lateral lemniscus contains relay nuclei of the auditory pathway in which the neurons have been grouped into dorsal and ventral (VNLL) nuclei. The data about the cytoarchitecture of the VNLL are controversial and no agreement exists concerning its tonotopical organization. In this paper, the cytoarchitecture of VNLL and the spatial distribution of its neurons projecting to the central nucleus of the inferior colliculus (CNIC) have been studied by using different tracers. Rats were iontophoretically injected in the CNIC and grouped in three sets. Group 1 rats received large injections of biotinylated dextran amine (BDA). Group 2 animals received restricted single injections of BDA in the low-, medium-, or high-frequency regions of the CNIC. Group 3 rats were double injected, with horseradish peroxidase placed in the high-frequency region of the CNIC, and with biocytin in the low-frequency one. The distribution of retrogradely labeled neurons in the ipsilateral VNLL was three-dimensionally reconstructed by use of a computer microscope. The analysis of labeled neurons and Nissl material suggests that the VNLL contains flat stellate neurons. Labeled flat stellate neurons and fibers are oriented in parallel and form fibrodendritic laminae. The projection from the VNLL to the CNIC is topographically organized: neurons in peripheral laminae project to dorsolateral, low-frequency regions of the CNIC, and those of central laminae project to ventromedial, high-frequency regions. Each VNLL lamina forms a continuous ventrodorsal structure which resembles a helicoid.

Immunohistochemical localization of oviductin in the endometrial lining of the golden hamster (Mesocricetus auratus) during the estrous cycle and early gestation

Oviductal non-ciliated secretory epithelial cells, under hormonal stimulation, synthesize and secrete a family of glycoproteins referred to as oviductins. These glycoproteins are found in oviductal fluid in several mammalian species, and have been localized in the oviduct, and in the zona pellucida of ovulated oocytes. In the golden hamster, this glycoprotein is named hamster oviductin-I. Recently, an immunofluorescent study on hamster uterine tissue has revealed the presence of the glycoprotein in luminal epithelial cells in a heterogeneous labelling pattern during the estrous cycle. The mechanism of endometrial epithelial cell receptivity to hamster oviductin-1 is not known. In this study, immunohistochemical studies were performed using a monoclonal antibody against the oviductin in conjunction with silver enhancement technique, in an attempt to determine further the factors playing a role in uterine receptivity to oviductin-1. Paraffin sections of hamster uterus obtained from different stages of the estrous cycle and from days 1-6 of gestation, and paraffin sections of hamster oviduct obtained from days 1-6 of gestation were used in this study. The results we obtained using the silver enhancement technique show that hamster uterus luminal epithelial cells exhibit a homogeneous, high intensity immunolabelling pattern throughout the estrous cycle, whereas, during gestation, labelling intensity decreases as the period for blastocyst implantation approaches. Oviduct epithelial cells revealed no definite fluctuating pattern in immunolabelling intensities during gestation, indicating no change in synthesis and secretion of the glycoprotein during this period. It is speculated that receptors for hamster oviductin-1 are present at the apical cell surface of endometrial cells and that implantation of the developing blastocyst into the uterine wall is possible only following downregulation of these receptors. The use of the silver enhancement technique proves to be an effective tool in immunohistochemical studies at the light microscope level, as seen through this study.

Functions of proteins secreted by oviduct epithelial cells

Studies on embryonic development in vitro as well as observations in vivo, suggested that two aspects of oviduct physiology are important for early development. On one side has to be considered the oviduct "environment": temperature, pH, osmotic pressure, nutrients, oxygen tension, free radical scavengers, etc. On the other, the oviduct "active components": stimulatory and/or regulatory molecules, supposed to finely regulate the fertilisation process and the first differentiative steps. While the physical environment of the oviduct has been under investigation for some decades, studies on oviduct-specific molecules and their functions have only been developed much more recently. The amount of information on this topic, however, has rapidly reached the size that demands a summary. In this review the descriptive literature on oviduct specific proteins will be examined as a basis for illustrating the possible functions of these molecules. In particular their role in fertilisation and early embryonic cleavages will be analysed in some details. Finally a section is devoted to the presence and physiological significance of growth factors in oviduct fluid.

A human oviduct-specific glycoprotein: synthesis, secretion, and localization during the menstrual cycle

The major objective of this study was to examine the hormonal regulation of a human oviduct-specific glycoprotein (huOGP) throughout the menstrual cycle and in all regions of the human oviduct. Regulation of synthesis and secretion was examined at both the protein (Western immunoblots and immunocytochemistry) and mRNA (Northern and slot blots) levels and correlated with changes in the morphological features of the oviductal epithelial cells throughout the cycle. Immunoblot analysis of oviductal fluid and explant culture media from all regions of the oviduct demonstrated that huOGP is primarily found during the follicular stage of the cycle and is not present in serum, follicular fluid, or uterine endometrium. Moreover, two-dimensional (2-D) immunoblots showed that all major isoelectric variants of huOGP observed on 2-D fluorographs are immunologically related. Light microscopic immunocytochemistry localized huOGP to oviductal secretory cells in both ampulla and isthmic regions, with the most intense immunoperoxidase staining seen in midcycle samples. Using an indirect immunogold technique at the electron microscopic level, huOGP was specifically localized to secretory granules of the ampullary and isthmic nonciliated epithelial cells. The ultrastructural characteristics of these secretory cells during the mid to late follicular phase of the cycle suggested elevated protein synthetic activity. In addition, mRNA expression for huOGP was elevated in all regions of the oviduct in midcycle specimens. Collectively, these data indicate that huOGP is a major tissue-specific, stage-specific secretory product of the human oviduct during the periovulatory stage of the cycle and support the hypothesis that huOGP synthesis and secretion may be regulated by fluctuations in the levels of estrogen and progesterone.

Elaboration of an oviductin by the oviductal epithelium in relation to embryo development as visualized by immunocytochemistry

The hamster oviduct secretes a high molecular weight antigen that belongs to the family of glycoproteins known as oviductins. In the present study, using immuno-electron microscopy, we examined the location of this hamster oviductin-1 (Hm Ov-1) in hamster oviductal oocytes and early embryos up to the blastocyst stage. The immunoreactive pattern of Hm Ov-1 changes markedly during the embryo development. In oviductal oocytes prior to fertilization, Hm Ov-1 was associated exclusively with the zona pellucida. Following fertilization, immunolabeling was detected in the perivitelline space and over the plasma membrane of 2-cell, 4-cell, and 8-cell embryos as well as young blastocysts. The change of the immunoreactive pattern was accompanied by the formation of an abundant number of coated pits, endocytic vesicles, multivesicular bodies, and lysosomal-like structures which were strongly labeled by gold particles. These immunogold-labeled cytoplasmic organelles characteristic of the endosomal-lysosomal apparatus were particularly evident in 2-cell, 4-cell, and 8-cell embryos and showed a decrease in number in the blastocysts. The close resemblance between the labeled flocculent material detected in the perivitelline space and that found in the zona matrix of early embryos and blastocysts suggested that the Hm Ov-1-associated electron-dense, flocculent material in the perivitelline space originated from the zona pellucida and was later endocytosed by the blastomeres through coated pits and endocytic vesicles. The detection of Hm Ov-1 in numerous multivesicular bodies and lysosomal structures indicated that the oviductin is eventually degraded. Although the exact functional role of Hm Ov-1 is not known, the presence of a copious amount of Hm Ov-1 in early hamster embryos may be ascribed to a special relationship between this particular oviductin and embryo development.

Stage-specific immunolabeling for oviductin in the secretory granules of the oviductal epithelium of the golden hamster during the estrous cycle

BACKGROUND

We have previously localized an antigen of oviductal origin in the zona pellucida of postovulatory hamster ova. This antigen is a high molecular weight glycoprotein secreted by the non-ciliated secretory cells of the oviduct and is later transferred to the zona pellucida of the oocyte during oviductal transit. This glycoprotein is rich in N-acetyl-D-galactosamine residues and has been designated Hamster Oviductin-1. In the present study, a monoclonal antibody (MAb) raised against this oviductin was used to detect the presence of this antigen in oviductal tissue during the estrous cycle.

METHODS

Twenty mature female golden hamsters were used and were divided into five groups of five animals each according to the five different stages of the estrous cycle. Quantitative immunocytochemistry was performed on MAb-labeled thin sections of Lowicryl-embedded ampullary region of hamster oviducts. Control experiments were also carried out to assess the specificity of the immunolabeling.

RESULTS

Quantitative analysis of the immunogold labeling indicated that maximum labeling for oviductin in the secretory granules of oviductal epithelial secretory cells was found around the time of ovulation, i.e., at estrus. The intensity of immunolabeling decreased from metestrus to diestrus 1, was at a minimum at diestrus 2, and started to increase at proestrus.

CONCLUSION

Together, these quantitative results indicate that expression of oviductin in the secretory granules of the hamster oviductal secretory cells is stage specific. Maximum labeling for the antigen coincides with the time of ovulation suggesting an important role for the oviductal epithelium in contributing its secretory product to the zona pellucida of oocytes freshly released from the ovary. Since the oviduct is the site of sperm-egg interaction and where fertilization and early embryo development take place, the maximal production of oviductin at the time of ovulation may facilitate some of these crucial steps during the intricate process of reproduction.

Ultrastructural localization of lectin receptors in the preimplantation ovine embryo

BACKGROUND

Preimplantation development of mammalia is characterized by cell surface changes functioning in intercellular communication and adhesion. The glycoconjugate role in cellular interactions has been analysed for several groups but not in sheep embryos. The binding patterns of eleven lectins during sheep preimplantation development were investigated and the role of glycoconjugates in early development was discussed.

METHODS

Ultrathin sections from preimplantation ovine embryos (3-7 days) were incubated with different colloidal gold conjugated lectins and the frequency of gold particles on the cell membrane, some organelles, and the zona pellucida was evaluated.

RESULTS AND CONCLUSIONS

We observed a higher staining of WGA, DBA, and SBA lectins in the intercellular contact zone with respect to the free cell surface of blastomeres during cleavage. This indicates that the N-acetyl galactosamine and N-acetyl glucosamine residues may be involved in sheep morula compaction. In contrast, the trophoblast cell displays an increase of staining of some lectins previously identified during cleavage (LcH, WGA, SBA, MPA, and PNA) on the free membrane, and a lack of sugar residues in the intercellular surface. This polarization of the trophoblast cell surface is not observed in the inner cell mass and could provide a mechanism for differentiation within the blastocyst. Intracytoplasmic vesicles show a cytochemical identity with lysosomes in the blastocyst (abundant GlcNAc and Man/Glc residues) that may reflect a functional relationship between both organelles in an intracellular cycle. The zona pellucida presents abundant GalNAc, GlcNAc, and Gal residues during preimplantation ovine development.

Affinity binding of hamster oviductin to spermatozoa and its influence on in vitro fertilization

The aim of this study was to determine the influence of hamster oviductal glycoprotein (oviductin) on in vitro gamete interaction. Oviductin was purified from the oviducts using lithium 3,5-diiodosalicylate, followed by phenol extraction. Immunocytochemistry using indirect fluorescence staining revealed that oviductin binds to the sperm anterior acrosomal region. The specific binding of oviductin resulted in inhibition of in vitro fertilization in studies using cumulus-free oocytes. The inhibitory effect was dependent on the concentration of oviductin and occurred in both ovarian and oviductal oocytes but not zona-free oocytes, indicating that sperm-zona interaction was interferred by oviduction. However, the inhibitory effect of oviductin in sperm-zona interaction was reduced when cumulus-enclosed oocytes from ovaries and oviducts were used, indicating that the egg investment including cumulus oophorus has some effect on oviductin-sperm complex and maintaining the fertilizing ability.

In vitro incubation of golden (Syrian) hamster ovarian oocytes and human sperm with a human oviduct specific glycoprotein

The objective of this study was to determine if human oviduct specific glycoprotein (huOGP) would associate with hamster ovarian oocytes and human sperm during in vitro incubation. The huOGP used in these studies was partially purified from human hydrosalpinx fluid. Hamster ovarian oocytes and human sperm samples were incubated in culture medium with and without huOGP. Association of huOGP was assessed by indirect immunofluorescence assay using a polyclonal antibody prepared against huOGP. Intense fluorescence of the zona pellucida, and bright but uneven fluorescence of the perivitelline space, were observed in hamster ovarian oocytes following incubation in the presence of huOGP. A similar but more uniform pattern of fluorescence was observed when hamster oviductal oocytes (positive controls) were incubated in culture medium alone. Fluorescence was absent when oocytes were assayed with preimmune serum. The association of huOGP with the zona pellucida and perivitelline space appeared to be specific since thyroglobulin, a large molecular weight glycoprotein, and human serum albumin, the major protein in oviduct fluid, did not associate with the hamster oocytes nor inhibit huOGP association when included in the culture medium. Fluorescence was absent when human sperm incubated with huOGP were assayed with antiserum to huOGP. However, human sperm fluoresced when incubated with a uterine glycoprotein, CUPED, which had previously been shown to bind to cat sperm during in vitro incubation. Sperm also fluoresced brightly when human sperm antibody was used as a positive control. Solubilization of sperm membrane proteins postincubation and analysis of these proteins by 1-D SDS-PAGE followed by immunoblotting also failed to show an association of huOGP with human sperm. Electron microscopy of sperm both pre- and postsolubilization confirmed that the sperm membranes were removed by this process. In conclusion, the association of huOGP with hamster oocytes in vitro suggests that huOGP may associate with human oocytes in vivo, whereas that may not be true for human sperm in vivo. The association of huOGP with oocytes may serve to facilitate the process of fertilization and early embryonic development within the oviduct.

Homogeneity in the distribution of matrix components in the hamster zona pellucida as revealed by backscattered electron imaging fracture-label

BACKGROUND

Backscattered electron imaging fracture-label (BEI-FL), an adaptation of the fracture-label method for scanning electron microscopy, offers the advantage of providing information about the distribution of antigenic and receptor sites with respect to the three-dimensional organization of tissues and cells over relatively large surfaces. Recently, using post-embedding cytochemistry on thin-sections of Lowicryl-embedded oocytes, a homogenous distribution of glycoproteins in the zona pellucida (ZP) was demonstrated (Kan et al., 1989. Biol. Reprod., 40:585-598, Anat. Rec., 226:37-47; Roux and Kan, 1991. Anat. Rec., 230:347-360). However, it can be argued that the chemical nature of resins and the physical conditions of tissue processing required for post-embedding cytochemistry may introduce changes in the tissue components and result in altered distribution of components. On the other hand, freeze-fracture exposes constituents in a minimally denaturing manner and, since no embedding media are used, binding sites are sterically available to the probe. We have, therefore, applied BEI-FL to examine the distribution of matrix glycoproteins in the ZP of hamster oocytes.

METHODS

Ovaries and cumulus masses obtained from superovulated female golden hamsters were fixed by immersion in 2.5% glutaraldehyde and processed for fracture-label. Tissues were labeled, respectively, with Wheat germ agglutinin (WGA) followed by ovomucoid-colloidal gold, Ricinus communis agglutinin I (RCA I)-colloidal gold or a monoclonal antibody against Hamster Oviductin-1 followed by protein A-gold, and then examined in the scanning electron microscope.

RESULTS

Backscattered electron imaging revealed a homogenous distribution of WGA and RCA I binding sites throughout the cross-fractured matrix of the ZP of ovarian and postovulatory oocytes. Hamster Oviductin-1, an oviductal glycoprotein which is transferred to the ZP of oocytes during oviductal transit, was also found to be uniformly distributed throughout the ZP of postovulatory oocytes.

CONCLUSIONS

Our results indicate that BEI-FL can be advantageously used to examine extracellular matrices and are consistent with the concept that glycoproteins are uniformly distributed throughout the ZP of the hamster oocyte.

Immunocytochemical localization of oviduct-specific glycoproteins in the oviductal epithelium from cows at follicular and luteal phases

The immunocytochemical localization of bovine oviduct-specific glycoproteins was investigated by light and electron microscopy. Using monoclonal antibodies (MAbs) specific for bovine oviductal glycoproteins, 3 regions (fimbriae, ampulla, and isthmus) of the epithelium in the bovine oviduct we studied during the follicular and luteal phases. The MAbs reacted specifically with the oviductal epithelial cells. Intense labeling was observed in the ampullar and fimbrial epithelia of cows at the follicular phase, but the reactions were weaker at the luteal phase. In the isthmus, the immunohistochemical reaction was faint during both follicular and luteal phases. At the ultrastructural level, the MAbs bound selectively to putative secretory granules of nonciliated cells in the ampulla and fimbriae, but not in the isthmus. These results suggest that there are cyclic changes and regional differences in the production of glycoproteins in the bovine oviduct.

Production and characterization of monoclonal antibodies specific for bovine oviductal glycoproteins

Four monoclonal antibodies (MAbs) were produced in rat cells against materials obtained from the bovine oviduct. The MAbs (1H10, 2A4, 2C5, and 1B12) reacted strongly with the oviductal epithelium of cows in the follicular phase. An immunohistochemical study demonstrated that each of the MAbs bound strongly to the supranuclear cytoplasm of epithelial cells of the oviduct, but not of the stromal cells. Antigens that reacted with the MAbs were characterized by immunoblotting analysis of proteins after fractionation by SDS-PAGE under reducing conditions of oviductal flushings obtained from cows at estrus. All MAbs strongly stained a band of protein with a molecular weight (MW) of 85-97 kD. MAb 1H10 also reacted with the minor band of a 55-kD protein. Similar antigens were not detected in uterine flushings, follicular fluid, and serum. No specific immunohistochemical reactivity with the MAbs was observed with other tissues from the reproductive tract and with nonreproductive tissues. The immunohistochemical reactions were completely eliminated by pretreatment of tissues with trypsin, but not with periodic acid, results that suggest that the antigenic determinants that react with the MAbs were proteinaceous rather than carbohydrate. We have thus established clones that produce 4 MAbs that are specific for oviduct-specific glycoproteins of the cow.

The zona pellucida binds the mature form of an oviductal glycoprotein (oviductin)

The use of a monoclonal antibody (MAb) specific for the oviductal zona pellucida (ZP) of the hamster has demonstrated that a new antigen (oviductin) is acquired by the ZP during transit of the oocyte in the oviduct. The epitope that is recognized by the MAb bears a terminal N-acetyl-D-galactosamine residue. We conducted a study in order to determine whether this immunoreactivity of the oviductal ZP results from the addition of the terminal sugar residue to a preformed ZP protein or from the transfer of the mature glycoprotein produced by oviductal secretory cells. We measured the incorporation of [35S]methionine into proteins using four different incubation systems: cumulus oophorus (CO) alone, CO in the presence of oviductal fluid, CO co-incubated with empty oviducts, and CO within intact oviducts. At the end of the incubation period, the ZP, vitelli, dispersed cumulus without oocyte, oviducts, and culture medium were isolated and analyzed for their protein content by sodiumdodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), autoradiography, and immunodetection. The cumulus cells synthesized several proteins, independently of the oviductal environment; however, none of these proteins corresponded to oviductin. The ZP and the vitelli of cumulus oophorus that were incubated either alone or in the presence of oviductal fluid did not contain radioactive oviductin. When the oviduct (empty or intact) was present in the incubation system, radiolabeled oviductin was synthesized and secreted into the incubation medium. The ZP picked up a detectable amount of radioactive antigen only in the system in which intact oviducts were incubated.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth and differentiation of the cultured secretory cells of the cow oviduct on reconstituted basement membrane

Isolated bovine oviduct epithelial cells were cultured on plastic precoated with matrigel. The epithelial cells seeded on 10 mg/ml matrigel often organized themselves into hollow tubes or spheres with microvilli directed towards the lumen. This is the first report of describing the spontaneous tube formation of oviduct epithelial cells in vitro. The epithelial cells growing on this substratum became fully differentiated with the formation of junctional complexes and the production of secretory vesicles which migrated to apical plasmalemma. Epithelial cells seeded on 2 mg/ml matrigel (dry film) formed a subconfluent monolayer in 15-20 days after seeding. The histoarchitecture of the secretory cells growing on the matrigel dry film closely resembled that of intact epithelial cells. Occasional ciliated cells containing large numbers of mitochondria were observed in cell colonies growing on 2 mg/ml matrigel but they possessed very few intact cilia. The monolayer linearly incorporated 35S-methionine into proteins up to 8 hr in presence of estradiol or progesterone. The fluorography of the newly synthesized proteins indicated that the cell extracts of estradiol-stimulated cells contained an additional protein of approximate molecular weight of 60 kd as compared to the extracts of cells incubated without steroids or incubated with progesterone.

Distribution of lectin receptors sites in the zona pellucida of follicular and ovulated rat oocytes

Carbohydrates of the zona pellucida (ZP) in mammals are believed to have a role in sperm-egg interaction. We have characterized the biochemical nature and distribution of the carbohydrate residues of rat ZP at the light (LM) and electron microscope (EM) levels, using lectins as probes. Immature female rats were induced to superovulate and cumulus-oocyte complexes were isolated from the oviduct, fixed with glutaraldehyde, and embedded in araldite for LM and LR-Gold for EM histochemistry. For examination of follicular oocytes, rat ovaries were fixed with glutaraldehyde and embedded in paraffin. The araldite or paraffin sections were deresined or deparaffinized, respectively, labeled with biotin-tagged lectins as probes, and avidin-biotin-peroxidase complex as visualant. For EM examination, thin LR-Gold sections were labeled with RCA-I colloidal gold complex (RCA/G) and stained with uranyl acetate. LM analyses indicate that in ovulated oocytes the ZP intensely binds peanut agglutinin (PNA); succinylated wheat germ agglutinin, (S-WGA), Griffonia simplisifolia agglutinin-I (GS-I) and soybean agglutinin (SBA), and to a lesser extent, lectins from Ricinus communis (RCA-I), Concanavaia ensiformis (Con A), Ulex europoeus (UEA-I), and wheat germ agglutinin (WGA). The neighboring cumulus cells are considerably less reactive and exhibit membrane staining only with Con A, WGA, and PNA. EM analysis of RCA/G binding revealed intensive binding to the inner layer region of the ZP and moderate binding to cytoplasmic vesicles of the cumulus cells. The ZP of follicular oocytes exhibits a different lectin binding pattern, expressed in staining strongly with PNA and S-WGA, and in a tendency of the lectin receptors to occur in the outer portion of the ZP.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes of glycoconjugate contents of the zona pellucida during oocyte growth and development in the golden hamster: a quantitative cytochemical study

We demonstrated here with the high resolution lectin-gold approach and quantitative analysis, changes of glycoconjugates in the hamster zona pellucida (ZP) during oocyte growth and development in the ovary and the oviduct. Glycoconjugates which contain N-acetyl-D-galactosamine as terminal sugar residues are absent in the ovary but are secreted by secretory cells in the oviduct and are added to the ZP of superovulated oocytes during oviductal transit. Glycoconjugates which carry sialic acid as terminal sugar residues appear to be acquired mainly from the ovary. The oviduct contributes little of this particular component to the ZP during the transit of oocytes in the oviduct. On the contrary D-galactose and N-acetylglucosamine associated glycoconjugates, added to the ZP in ovarian follicles, are also secreted by non-ciliated oviductal epithelial cells and these secretory products are transferred to the ZP in significant amount during passage of the oocyte through the oviduct. Lectin-gold labeling of the ZP of superovulated oocytes reveals homogeneous distribution of gold particles throughout the zona matrix. Thus, we conclude that the ZP of hamster superovulated oocytes consists of glycoconjugates that may derive from different origins. Deposition of ZP glycocomponents begins in the ovary. Similar and new glycoconjugates, secreted by oviductal non-ciliated secretory cells, are added to the ZP of oocytes during oviductal transit. At this stage the ZP is made up of a homogeneous matrix of glycoconjugates.

In vitro and in vivo association of an oviduct estrus-associated protein with bovine zona pellucida

The interaction between the bovine egg zona pellucida and a 97 kDa estrus-associated protein produced by the oviduct was examined in vitro and in vivo. In vitro matured bovine eggs were incubated with oviduct fluid recovered throughout the estrous cycle from separate indwelling cannulae placed in the ampulla and isthmus of the same oviduct. Immunofluorescence techniques and a polyclonal antiserum against the 97 kDa protein were used to localize this protein on washed eggs previously incubated with oviduct fluid. Intensity and distribution of immunofluorescence varied with stage of cycle and to a lesser degree with region of oviduct from which the oviduct fluid was obtained. The most intense fluorescence was observed on the zonae pellucidae of eggs incubated with oviduct fluid pooled from days near estrus and ovulation compared to fluid pooled from luteal stage days. The immunofluorescence of isthmus-derived oviduct fluid was more intense than was ampulla-derived oviduct fluid collected near estrus. The zonae pellucidae of 7-day-old embryos flushed from the uterus displayed immunofluorescence comparable to that observed on the zonae pellucidae of eggs incubated in vitro with peri-estrus oviduct fluid. No immunofluorescence was observed associated with the perivitelline space, egg cytoplasm, or blastomeres. The apparent uptake of a 97 kDa estrus-associated protein by the zonae pellucidae of eggs in vitro and embryos in vivo may indicate that this protein functions in fertilization and/or early embryo development.

High-resolution localization of hyaluronic acid in the golden hamster oocyte-cumulus complex by use of a hyaluronidase-gold complex

The distribution of hyaluronic acid in the oocyte-cumulus complexes collected from the oviduct ampulla of superovulated hamsters was revealed by use of hyaluronidase coupled to colloidal gold. On thin sections of Lowicryl-embedded oocyte-cumulus complexes, gold particles were associated specifically with interconnecting fibrillar materials that make up the cumulus matrix. Inside the cumulus cells, gold particles were found over the cisternal membrane of the rough endoplasmic reticulum, in the contents of lysosomes and multivesicular bodies, and over Golgi vesicles of some cumulus cells. A high concentration of gold labeling was observed over the peripheral condensed chromatin and perinucleolar components in the nucleus. The cell surface of the cumulus cells also appeared to be labeled. Gold particles, however, were absent over the mitochondria and lipid vacuoles. In the oocytes, labeling was found to be associated mainly with rough endoplasmic reticulum and arrays of lamellar structures; cortical granules, mitochondria, and coated vesicles were essentially devoid of gold particles. Gold particles were also seen along the plasma membrane of the oocytes and within the perivitelline space. The zona pellucida was not labeled by hyaluronidase-gold. Different control experiments confirmed the specificity of the labeling. Digestion of thin sections with hyaluronidase prior to incubation with hyaluronidase-gold abolished the initial reaction, whereas treatment of thin sections with chondroitinase did not prevent labeling of oocyte-cumulus complexes by hyaluronidase-gold. Although the function of hyaluronic acid in the oocyte-cumulus complex at the time of ovulation and fertilization is not known, the high concentration of this particular compound in the cumulus matrix and the cumulus cells and its specific locations in the perivitelline space and in the superovulated oocytes implicate the significance of its presence and warrant future investigations.